The Arizona Republican and Colorado Democrat also visited Rocky Mountain National Park, where they viewed trees killed by the pine bark beetle, The Denver Post reported Tuesday. The senators are on a bi-partisan tour of the west that included a two-day weekend visit to the Grand Canyon.
At Monday's hearing, Alice Madden, an expert on climate working for Colorado Gov. Bill Ritter, said pine bark beetles are spreading because of warmer temperatures. She said beetles have already killed 2.5 million acres of lodge pole, Ponderosa and limber pines.
McCain is a longtime supporter of nuclear power. Udall said he now agrees with him.
"It is clear that if we want to respond to climate change, nuclear power has to be part of the solution," Udall said.
McCain urged the Obama administration to make climate change its next priority after health care.